Domestic water treatment devices are known in the art. They include in-line devices (e.g., under the sink), terminal end devices (e.g., counter top or faucet mounted), and self-contained systems which process water in batches. Examples of batch devices are pitchers/carafes and larger reservoirs where treated water is poured for example from a spigot. Batch water treatment systems can also be incorporated into other devices, such as a coffee maker. These self-contained systems typically have upper and lower chambers separated by a filter cartridge. They rely on gravity to force water from the upper chamber, through the cartridge, and into the lower chamber, thereby producing treated water.
Mechanical filters, which treat water by preventing particulates from passing through them, provide a ready end-of-life indication through reduced flow due to particulate accumulation. Chemical removal media (e.g., charcoal based media and ion exchange media) employ processes such as adsorption and ion exchange for treating water. These processes do not reduce flow or provide other end-of-life indication.
Various approaches have been taken to provide end-of-life indication where it is not inherently provided by the media. It is known for example to "totalize," mechanically or electronically, the volume of water that has been treated. The mechanical approach typically involves a turbine and gear reduction mechanism. The electronic approach typically involves a pressure transducer and a microprocessor which integrates to calculate volume. Such systems are relatively expensive, however, and do not lend themselves well to batch treatment devices.
In batch treatment systems, it is known to approximate the amount of water that has been treated by counting the number of times the device has been filled. Such a prior art device is described in U.S. patent application Ser. No. 08/341,420, filed Nov. 17, 1994, which is expected to issue as a U.S. Patent shortly. The '341 fill-counting system employs a float which rotates one revolution on a threaded rod each time the device is filled. One short-coming of this approach is that there is no continuous visual indication of the amount of useful life remaining, but only an indication at the end of life.
Where relatively loose particle media are employed, such as the loose granular activated carbon and resins typically used in batch systems, media particles tend to come out of the cartridge with the treated water. Although ingesting these particles is generally not a significant health concern, consumers consider it undesirable to see what appears to be sediment in the treated water. An example of a gravity-fed system where this is a shortcoming is shown in U.S. Pat. No. 4,969,996.
What has been needed is a novel fill-counting mechanism which provides a continuous visual indication of the amount of useful life remaining in the filter cartridge. What has also been needed is a novel filter cartridge assembly which reduces the number of media particles in the treated water.